Tube socket voltage limiting apparatus and method of manufacturing the same

ABSTRACT

A voltage limiting apparatus for use in connection with a tube socket comprising a terminal contact adapted to comate with the pin of a tube. The apparatus preferably comprises a conductive member having a first portion adapted to be connected to a ground point and a second portion electrically connected to the contact. A gap is located between the first and second portions. A nonconductive piece of material rigidly positions the first portion with respect to the second portion so that the size of the gap remains constant, thereby causing the voltage at which an electrical discharge occurs across the gap to remain at a predetermined constant value. A method of manufacturing the apparatus includes the steps of fabricating a conductive member with the first and second portions, molding plastic to the conductive member to fix the positions of the two portions and then forming the electrical gap between the portions.

United 813168 Patent 1191 Borth 1 51 Feb. 13, 1973 s41- TUBE SOCKET VOLTAGE LIMITING 3,377,612 4/1968 Klier et al. ..339/143 '1 APPARATUS AND METHOD OF MANUFACTURING THE SAME Primary Examiner-Richard E. Moore [76] Inventor: Anthony Borth, Rural Rt. 1, Moroc- [57] ABSTRACT co, 1nd. 47963 A voltage limiting apparatus for use in connection [22] Ffled: April 1970 with a tube socket comprising a terminal contact [21] Appl. No.: 25,995 adapted to comate with the pin of a tube. The apparatus preferably comprlses a conductwe member having a first portion adapted to be' connected to a [52] U.S. Cl. ..339/l43 T, 339/193 R, 339/218 L ground point and a second rtion electrically con- CL ..H01l' nccted to the ontact A gap is located between the Fleld of Search 111, first and second portions. A nonconductive piece of 339/198 313/325, 331 material rigidly positions the first portion with respect to the second portion so that the size of the gap References Cited remains constant, thereby causing the voltage at which an electrical discharge occurs across the gap to remain UNITED STATES PATENTS at a predetermined constant value. A method of 3,553,727 1/1971 Leimontas etal. ..313/325 manufacturing the apparatus includes the Steps of 3,502,933 3 1970 Leimontas etal.....-. ..313 325 fa ricating a c nductive member with the first and 3,466,491 9/1969 Momberger ..3l3/331 second portions, molding plastic to the conductive 3,543,098 11/1970 S vits et al. ..3l7/l0l member to fix the positions of the two portions and 3,227,910 1/1966 Pittman 339/193 X then forming the electrical gap between the portions. 2,509,701 5/1950 Smith, Jr ..339/l98 E 3,251,016 5/ 1966 Manetti et a1. ..339l193 X 8 Claims, 11 Drawing Figures 60 72 77 93 64 8 55 67 36 /08 4 4' 98 3. i as 26 34- /6 56 22 40 l I I 1 42 a0 2 l4 /a 20 3 123 I a I /aa PAT ENTED FEB 1 31913 SHEET 2 or 2 T m n w N w T. N A

AT T OPNEW TUBE SOCKET VOLTAGE LIMITING APPARATUS AND METHOD OF MANUFACTURING THE SAME BACKGROUND OF THE INVENTION It is well known that certain kinds of electronic tubes, such as cathode ray tubes and television picture tubes, occasionally generate large transient voltages within the tube. Unless these voltages are controlled or dissipated, they may be conducted through the tube pins and tube socket contacts to other portions of the circuitry associated with the tube. If a large transient voltage reaches the associated circuitry, it can cause great damage.

In the past, there have been attempts to provide protection against such large transient voltages by placing a grounded strip of metal adjacent each tube contact. According to this method, voltage discharges or arcs across the space between a contact and its associated strip when the contact potential builds-up to a predetermined value, thereby dissipating the excessive voltage and protecting the associated circuitry. An example of this approach is illustrated in U.S. Pat. No. 3,251,0l6, issued May 10, I966 in the names of F. P. Manetti et al., and U.S. Pat. No. 3,377,612, issued Apr. 9, 1968 in the namesof L. Klier et al.

Although the teaching of these patents appears to work in theory, practical experience has indicated that it has a number of deficiencies that limit its overall usefulness. For example, devices of the type described by Manetti et al. and Klier et al. are generally not able to precisely control the maximum voltage on a contact. Applicant believes that this deficiency results primarily fromv the manner in which the contacts and strips are arranged. Applicants experience has shown that the size of the space between the contact and grounded strip in such devices frequently changes due to the stress of handling and shipping, and due to the disturbance created by. inserting the pins of the tube in the contacts during assembly or repair. Moreover, the size of the space is difficult to adjust precisely during assembly, and generally requires time-consuming effort by a skilled technician.

This defect in operation renders the Manetti et al. and Klier et al. type of protection device unreliable and difficult to adjust primarily because the slightest change in the size of the spacebetween the contact and the strip drastically alters the voltage at which discharge takes place. Basically, the discharge voltage increases as the distance between the contact and strip increases, and decreases as the distance decreases. In order to provide reliable operation, applicant has learned that even minute changes in the space must be avoided, since a change of only 0.001 inch results in a change of about 100 volts in the discharge voltage. Thus if the space widens by only a few thousandths of an inch, the voltage on a contact is allowed to buildup to excessive values, thereby endangering associated circuitry. Likewise, if the space decreases by only a few thousandths of an inch, discharge occurs at a relatively low voltage, thereby maintaining the contact at a voltage too low to optimize operation of the tube.

Accordingly, it is a primary object of the present invention to provide improved apparatus for controlling the maximum potential of a tube socket contact in which no adjustment is required during assembly of the socket.

It is yet another object of the present invention to provide improved apparatus of the type indicated in which the maximum potential to which a tube socket contact can build-up remains at a relatively constant value during the life of the socket.

Still another object of the present invention is to provide improved apparatus in which the size of a gap used to controlthe discharge voltage of a tube socket contact does not vary during shipping, installation, or rough handling.

It is still another object of the present invention to provide improved apparatus in which the discharge of voltage of a tube socket contact is controlled by a gap placed in a conductive member that is encapsulated in a nonconductive material.

Yet another object of the present invention is to provide improved apparatus in which a gap that controls the maximum potential of a tube socket contact may be established prior to assembly of the tube socket.

Still another object of the present invention is to provide improved apparatus whereby the maximum potential of a tube socket contact may be conveniently altered as desired.

Yet another object of the presentinvention is to provide an improved method of manufacturing and assembling apparatus of the foregoing type.

SUMMARY OF THE INVENTION The present invention is preferably used in connection with a tube socket comprising at least one terminal contact adapted to comate with the pin of'an electronic tube so that the maximum potential on the contact relative to a ground point is accurately controlled. In such an environment, a principal feature of the apparatus aspect of the invention comprises a conductive member having a first portion that is adapted to be electrically connected to the ground point and a second portion that is electrically connected to the tube contact. Means are also provided for rigidly positioning the first and second portions with respect to each other, such as by encapsulating the conductive member in a plastic material. A gap placed in the conductive member is then maintained at a uniform size. As a result, the maximum voltage which can build up on the contact is maintained at a precise, predetermined value.

Another aspect of the invention relates to an improved method of manufacturing apparatus of the type described. According to the preferred method, a socket housing including a contact is fabricated and wired. A conductive member is then fabricated and encapsulated in a shaped mass of nonconductive material. A gap having a predetermined size is then formed in the conductive member, and the shaped mass is fitted into the housing to form a completed assembly.

The advantages of using apparatus and manufacturing methods in accordance with the foregoing principles are at once apparent. Since the discharge gap is positioned between two portions of a conductive member that are rigidly held with respect to eachother, the size of the gap remains constant even though the tube socket is subjected to rough handling and even though the tube contacts are repositioned during the insertion of tube pins therein. As a result, the maximum permissible voltage on the contact can be established and maintained at a predetermined value with a. degree of accuracy heretofore unattainable. Likewise, in accordance with another feature of the invention, the gap may be economically and accurately fabricated in the conductive member by using ordinary punching dies after the conductive member is encapsulated. When this procedure is used, there is no need to adjust the discharge gap during assembly or usage. The discharge voltage may be easily adjusted by using any desired size of dies during the punching operation. Accordingly, the cost of manufacturing the resulting tube socket is significantly reduced.- In addition to the foregoing advantages, the encapsulated and gapped conductive member may be tested for its voltage-limiting characteristics before being assembled into the socket, thereby improving quality control. Moreover, repair in the field is easily achieved by merely substituting one encapsulated conductive member for another.

BRIEF DESCRIPTION OF THE DRAWINGS These and other objects, advantages and features of the present invention will hereinafter appear, for purposes of illustration, but not of limitation, in connection with the accompanying drawings, wherein like numbers refer to like elements throughout, and wherein:

FIG. 1 is aperspective view of a tube socket made in accordance with the present invention;

FIG. 2 is across-sectional view taken along line 22 in FIG. 1;

FIG. 3 is a cross-sectional view taken along line 3--3 in FIG. 2;

FIG. 4 is a perspective, exploded view of the tube socket shown in FIG. 1;

FIG. 4A is an enlarged, perspective view of a portion of the tube socket shown in FIG. 4;

FIG. 5 is a side elevational view of a preferred form of punching apparatus used to manufacture the tube socket;

FIG. 6 is a top plan view of the lower portion of the punching apparatus taken along line 66 in FIG. 5;

FIG. 6A is an enlarged view of a single one of the punches shown in FIG. 6;

FIG. 7 is a bottom plan view of the top portion of the punching apparatus taken along line 7-7 in FIG. 5;

FIG. 7A is an enlarged view of a single one of the dies shown in FIG. 7; and

FIG. 8 is an enlarged, perspective view of a preferred form of a conductive member as it appears prior to encapsulation and punching.

DESCRIPTION OF THE PREFERRED EMBODIMENT The preferred embodiment of a television picture Housing 8 also contains exemplary contacts 12 and 18 having axes 12a and 18a, respectively; More specifically, contact 12 comprises a hollow cylindrical portion 14 that is adapted to receive a tube pin, and a terminal clamp 16. Likewise, contact 18 comprises a similar hollow cylindrical portion 20 and a terminal clamp 22.

After housing 8 is molded and fitted with contacts in the manner indicated, a resistor 24 having a body portion 26 is assembled in the housing in the manner indicated in FIG. 2. More specifically, lead 28 is physically attached to terminal clamp 16 and lead 30 is at tached to a lead wire 40 by a clamp 44. A resistor 32 having a body portion 34 is also assembled in housing 8 in the manner shown in FIG. 2. More specifically, resistor 32 has a lead 36 that is physically connected to terminal clamp 22 and a lead 38 that is connected to a lead wire 42 through a clamp 46.

Of course, additional holes within hole group 10 may be fitted with contacts and resistors in the manner indicated in FIG. 2 as required. The contacts and resistors illustrated in FIG. 2 are merely exemplary of typical connections that may be made for contacts on which voltage protection is required.

Housing 8 also includes a flange 48 that is used to attach the rear housing 50 and including a series of holes 49.

As best shown in FIGS. 2-4A and 8, voltage protection assembly 54 comprises an integrally stamped, brass conductive member 62. The conductive member comprises a ring 64 that includes holes 66 and 67 which provide a means of connecting the ring to a ground point. Member 62 also comprises strips 68-77 that extend radially inward from ring 64. Fixtures 78-87 are attached to the inner ends of strips 68-77, respectively, and are oriented perpendicular thereto. Each fixture is identical and may be understood from exemplary fixture 82.

As best shown in FIGS. 2, 3 and 8, fixture 82 comprises two prongs 88 that extend outward from the surface of wafer member 60. As shown in FIG. 4A, when prongs 88 are forced over resistor lead 28, they bite into the surface of the resistor lead, thereby providing flexible and positive physical contact. As a result, even if contact 12 is bent and resistor lead 28 is rotated, the position of strip 72 is not substantially altered. This construction helps to maintain the gap in strip 72 at a precise size. The prongs may be easily removed from lead 28 by merely moving assembly '54 to the left of housing 8 as shown in FIG. 4. As a result, the protection assembly 54 may be conveniently removed for inspection and replaced without the need of unsoldering any leads or mechanically reconnecting any lead wires.

After conductive member 62 is formed, it is encapsulated by well known injection molding techniques. In accordance with these techniques, flame retardant polypropelene is injected into a mold in which member 62 is positioned in order to form a shaped plastic mass or piece 55. Piece 55 comprises a slotted collar 56 that defines a through center hole 57, a key 58, and a wafer member 60. The slots in collar 56 and key 58 fit into corresponding parts of housing 8 in order to insure proper assembly. During the molding process, wafer 60 is formed so that it defines holes 89-98 which expose both sides of strips 68-77,.respectively, and portions of ring 64 in the manner shown in FIG. 3. This is achieved by providing studs at appropriate positions in the mold.

When conductive member 62 has been encapsulated in the manner indicated, the punching apparatus 110 illustrated in FIGS. 5-7A are used to punch gaps 99-108 in strips 68-77, respectively. Apparatus 110 comprises a base 112 that bears punches 114, one of which is shown in detail in FIG. 6A. The apparatus also comprises an upper portion 116 that defines dies 118, one of which is shown in detail in FIG. 7A. Recess 120 is provided to mate with key 58. As shown in FIG. 3, holes 89-98 provide convenient access to the portion of the strip to be punched, thereby facilitating the punching operation. The dimensions of the punches and dies may be altered to accomodate a gap of various widths in order to control the maximum voltage that can be built up on a contact before discharge takes place across the gap. Of course, other more complicated methods of producing gaps 89-107 may be used. However, applicant has found that punching with the apparatus illustrated in FIGS. 5-7A produces a precisely dimensioned gap within close tolerances that is capable of providing a discharge voltage having an exact, predetermined value.

In order to complete the manufacture of the tube socket, the completed voltage protection assembly 54 is fitted into housing 8 that has been prewired in the manner indicated in FIG. 2. As the assembly is fitted into its proper position, the prongs on each fixture (e.g., prongs 88) are fitted over resistor leads, or the like, so that the inner portion of each strip is electrically connected to its corresponding socket contact. When the assembly is fitted into place, leads are connected and soldered to holes 66 and 67 so that ring 64 may be connected to a ground point during the assembly of associated circuitry. Finally, rear housing 50 is fitted onto front housing 8 with studs 53 extending through corresponding holes 49 in the manner shown in FIGS. 1 and 4.

Since the conductive member 62 is encapsulated in a plastic material before the gaps are punched therein, the various portions of the member are fixed in relationship to each other and the dimensions of the gaps remain constant even though the socket is subjected to rough handling and assembly procedures.

If the voltage protection assembly should need to be replaced for any reason, the rear housing may be easily removed and the assembly 54 withdrawn from the front housing without removing. any of the components fitted therein. Subsequently, a new or repaired assembly may be conveniently fitted into the front housing in the manner previously described without unsoldering any leads other than those connected to holes 66 and 67. Of course, this procedure greatly simplifies assembly and repair of the socket.

It should be recognized that the apparatus and methods described herein are merely exemplary of the preferred practice of the invention, and that various modifications and alterations of the apparatus and methods may be affected without departing from the spirit and scope of the invention as defined in the appended claims.

What is claimed is:

l. In a tube socket having a terminal contact adapted to comate with the pin of a cathode ray tube and a conductor connected to the contact, improved apparatus for controlling the maximum potential on said contact relative to a ground point, said apparatus comprising in combination:

a conductive ring;

a conductive strip extending radially inward from said ring;

conductive fixture means locatedat the inner end of said strip for removably connecting said strip to a conductor that is connected to said contact, said fixture comprising two prongs that fit on either side of said conductor;

means located on said ring for electrically connecting said ring to said ground point; and

a unitary plastic body in which said ring and said strip are embedded, said plastic body having a hole that exposes both sides of a predetermined portion of said strip, there being a gap in said strip located in the portion exposed by said hole, whereby the potential between said contact and ground point at which an electrical discharge occurs across said gap remains at a predetermined constant value.

2. A tube socket comprising:

a socket housing having a generally planar front surface with an annular array of tube pin holes therein, Contact cavities extending rearwardly from said holes and an annular wall extending rearwardly and located outside said cavities;

tube pin receiving contacts in said cavities having terminal portions extending rearwardly of the socket;

circuit elements outside said wall having opposed leads, one extending around the rear of said wall and connected with the terminal of the associated contact and the other extending forwardly within the socket;

a voltage protection assembly for said contacts having separate conductive portions connected with the portion of each of the circuit element leads extending around the rear of said wall; and

lead wires connected with the other leads of said circuit elements and extending outwardly from the socket.

3. A tube socket having an improved apparatus for controlling the maximum electrical potential on contacts, comprising:

a socket housing;

circuit means in said housing including contacts to receive the pins of an electron tube and conductive leads connected to each contact; and

a voltage protection spark gap assembly including a nonconductive support in said socket having a first conductive portion fixedly secured thereto for connection with an electrical reference potential and separate conductive portions each having a pair of spaced prongs which embrace a conductive lead connected with a tube pin receiving contact and electrically connecting each conductive portion with a conductive lead, each of said separate conductive portions being fixedly secured to said support and being spaced from said first conductive portion, forming spark gaps therewith having a fixed dimension.

4. A tube socket comprising:

a socket housing having a generally planar front surface with an annular array of tube pin holes therein, contact cavities extending rearwardly from said holes and an annular wall extending rearwardly and located outside said cavities;

I and tube pin receiving contacts in said cavities having" terminal portions extending rearwardly of the socket;

circuit elements outside said wall having opposed leads, one extending around the rear of said wall and connected with the terminal of the associated contact and the other extending forwardly within the socket;

lead wires connected with the other leads of said circuit elements and extending outwardly from the socket; and

a voltage protection assembly for said contacts having a first conductive portion and separate conductive portions each with a pair of spaced prongs embracing the portion of each of the circuit element leads extending around the rear of said wall, said separate conductive portions being fixedly positioned with respect to said first conductive portion forming spark gaps therewith having a fixed dimension.

5. The tube socket of claim 4 in which the rear face of said wall has slots and said spaced prongs extend into said slots.

6. A tube socket having an improved apparatus for controlling the maximum electrical potential on elements of a tube received by the socket, comprising:

a socket housing;

a plurality of circuits in said housing each including a contact to receive the pin of an electron tube and a conductive lead connected to the contact, said contacts being arranged to conform with the pins of the tube and said conductive leads extending out from the housing;

7 a voltage protection spark gap assembly including a rigid disc-shaped nonconductive support in said socket housing,

a ring-like metal element immovably held to the outer part of the support and extending therearound, for connection with an electrical reference potential, and

a plurality of metal legs immovably held to the support, each leg extending outwardly toward the ring-like metal element, each leg being electrically connected at its inner end with one of said circuits and through the circuit with an element of a tube received by the socket, the outer end of each leg having an exposed cross-sectional surface spaced from an opposed surfaceon said ring-like metal element, forming a spark gap between said surfaces, said ring-like element and legs being immovably held with respect to each other by said support whereby each spark gap has a fixed dimension, said support having a plurality of openings therethrough, said openings having a boundary surfacev located generally in alignment with and outwardly of the opposed surfaces, whereby the spark gaps are in air and away from the support, the like element and legs being immovably affixed to thesupport as a single piece and the legs having been severed from the ring-like element to form said spark gaps.

7. The tube socket of claim 6 in which the single metal piece comprising said ring-like element and said legs is encapsulated in said nonconduetive support.

8. In a tube socket having terminal contacts adapted to comate with the pins of a cathode ray tube and conductors connected to the contacts, improved apparatus for controlling the maximum potential on said contacts relative to a ground point, said apparatus comprising in combination:

a conductive ring;

a plurality of conductive strips extending radially inward from said ring, one for each contact on which the potential is to be controlled;

conductive fixture means located at the inner end of each strip for removably electrically connecting said strip to a conductor and to the associated contact;

means located on said ring for electrically connecting said ring to said ground point; and

a unitary plastic body to which said ring and said strips are secured, said plastic body having holes that expose both sides of a portion of each strip and of the ring adjacent thereto, there being a gap in each strip located in the portion exposed by said I hole, whereby thepotential between each contact and the ground point at which an electrical discharge occurs across said gap remains at a predetermined constant value, the ring and strips being secured to the plastic body as a single piece and the strips being severed from the ring to form the gaps. 

1. In a tube socket having a terminal contact adapted to comate with the pin of a cathode ray tube and a conductor connected to the contact, improved apparatus for controlling the maximum potential on said contact relative to a ground point, said apparatus comprising in combination: a conductive ring; a conductive strip extending radially inward from said ring; conductive fixture means located at the inner end of said strip for removably connecting said strip to a conductor that is connected to said contact, said fixture comprising two prongs that fit on either side of said conductor; means located on said ring for electrically connecting said ring to said ground point; and a unitary plastic body in which said ring and said strip are embedded, said plastic body having a hole that exposes both sides of a predetermined portion of said strip, there being a gap in said strip located in the portion exposed by said hole, whereby the potential between said contact and ground point at which an electrical discharge occurs across said gap remains at a predetermined constant value.
 1. In a tube socket having a terminal contact adapted to comate with the pin of a cathode ray tube and a conductor connected to the contact, improved apparatus for controlling the maximum potential on said contact relative to a ground point, said apparatus comprising in combination: a conductive ring; a conductive strip extending radially inward from said ring; conductive fixture means located at the inner end of said strip for removably connecting said strip to a conductor that is connected to said contact, said fixture comprising two prongs that fit on either side of said conductor; means located on said ring for electrically connecting said ring to said ground point; and a unitary plastic body in which said ring and said strip are embedded, said plastic body having a hole that exposes both sides of a predetermined portion of said strip, there being a gap in said strip located in the portion exposed by said hole, whereby the potential between said contact and ground point at which an electrical discharge occurs across said gap remains at a predetermined constant value.
 2. The socket of claim 1 including a voltage protection assembly for said contacts having separate conductive portions connected with the portion of each of the circuit element leads extending around the rear of said wall.
 3. A tube socket having an improved apparatus for controlling the maximum electrical potential on contacts, comprising: a socket housing; circuit means in said housing including contacts to receive the pins of an electron tube and conductive leads connected to each contact; and a voltage protection spark gap assembly including a nonconductive support in said socket having a first conductive portion fixedly secured thereto for connection with an electrical reference potential and separate conductive portions each having a pair of spaced prongs which embrace a conductive lead connected with a tube pin receiving contact and electrically connecting each conductive portion with a conductive lead, each of said separate conductive portions being fixedly secured to said support and being spaced from said first conductive portion, forming spark gaps therewith having a fixed dimension.
 4. A tube socket comprising: a socket housing having a generalLy planar front surface with an annular array of tube pin holes therein, contact cavities extending rearwardly from said holes and an annular wall extending rearwardly and located outside said cavities; tube pin receiving contacts in said cavities having terminal portions extending rearwardly of the socket; circuit elements outside said wall having opposed leads, one extending around the rear of said wall and connected with the terminal of the associated contact and the other extending forwardly within the socket; lead wires connected with the other leads of said circuit elements and extending outwardly from the socket; and a voltage protection assembly for said contacts having a first conductive portion and separate conductive portions each with a pair of spaced prongs embracing the portion of each of the circuit element leads extending around the rear of said wall, said separate conductive portions being fixedly positioned with respect to said first conductive portion forming spark gaps therewith having a fixed dimension.
 5. The tube socket of claim 4 in which the rear face of said wall has slots and said spaced prongs extend into said slots.
 6. A tube socket having an improved apparatus for controlling the maximum electrical potential on elements of a tube received by the socket, comprising: a socket housing; a plurality of circuits in said housing each including a contact to receive the pin of an electron tube and a conductive lead connected to the contact, said contacts being arranged to conform with the pins of the tube and said conductive leads extending out from the housing; and a voltage protection spark gap assembly including a rigid disc-shaped nonconductive support in said socket housing, a ring-like metal element immovably held to the outer part of the support and extending therearound, for connection with an electrical reference potential, and a plurality of metal legs immovably held to the support, each leg extending outwardly toward the ring-like metal element, each leg being electrically connected at its inner end with one of said circuits and through the circuit with an element of a tube received by the socket, the outer end of each leg having an exposed cross-sectional surface spaced from an opposed surface on said ring-like metal element, forming a spark gap between said surfaces, said ring-like element and legs being immovably held with respect to each other by said support whereby each spark gap has a fixed dimension, said support having a plurality of openings therethrough, said openings having a boundary surface located generally in alignment with and outwardly of the opposed surfaces, whereby the spark gaps are in air and away from the support, the like element and legs being immovably affixed to the support as a single piece and the legs having been severed from the ring-like element to form said spark gaps.
 7. The tube socket of claim 6 in which the single metal piece comprising said ring-like element and said legs is encapsulated in said nonconductive support. 